Yes, adds is a Scrabble word!

Verb

1. Make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of

2. State or say further

3. Bestow a quality on

4. Make an addition by combining numbers

5. Determine the sum of

6. Constitute an addition

Noun

1. A condition (mostly in boys) characterized by behavioral and learning disorders